1. Field of the Invention
The present invention relates generally to an antenna apparatus. More particularly, the invention relates to an antenna apparatus for use in mobile communications and local area networks (LAN).
2. Description of the Related Art
The construction of a known antenna apparatus will now be described with reference to FIG. 15. Referring to FIG. 15, an antenna apparatus generally designated by 91 has a substrate 92. The substrate 92, which is rectangular-prism shaped, is formed by stacking a plurality of ceramic sheets through, for example, a conductor (not shown), and is provided with a feeding terminal 93 and a fixing terminal 94 at a pair of opposedly-facing lateral surfaces, respectively. The feeding terminal 93 is disposed on the surface of the substrate 92 and is connected to the conductor, while the fixing terminal 94 provided for soldering is not electrically connected. The antenna apparatus 91 constructed as described above is placed on a printed wiring board 95, and the feeding terminal 93 and the fixing terminal 94 are soldered and fixed on the board 95.
However, the antenna apparatus 91 may be chipped or dropped and broken while being handled, and the characteristics of the antenna apparatus 91 may deteriorate due to the oxidation of electrodes or deformation of the members when the apparatus 91 is used under high temperatures and high humidity. Also, the antenna apparatus 91 is surface-mounted on the printed wiring board 95 and completely contacts on an overall surface with the board 95. Accordingly, the apparatus 91 may be deformed if there is a warp in the board 95. Further, the antenna apparatus 91 surface-mounted on the wiring board 95 is positioned in close proximity to the wiring on the wiring board 95. In particular, if the portion of the substrate 92 exhibiting intense directivity is mounted in proximity to the board 95, the directivity of the antenna apparatus 91 is influenced by a ground electrode, which may hamper the desired non-directivity of the apparatus 91. Additionally, if the apparatus 91 is located in proximity to the ground electrode, the capacitance (C) of the antenna line is increased and the inductance (L) is decreased, thus causing the antenna to deviate from a specific impedance (L/C). As a consequence, a desired return loss cannot be obtained and the bandwidth is decreased.